1. Field of the Invention
The present invention relates to semiconductor technology. More particularly, the present invention relates to a method and circuit for element wearout recovery.
2. Description of the Prior Art
It is well known in the semiconductor industry that certain physical properties associated with solid-state devices are subject to a variety of mechanical, electrical and/or chemical failure mechanisms. It is known that elements, such as, for example, transistors from both CMOS and Bipolar technologies, are susceptible during product use to certain reliability wearout mechanisms that can severely impact the efficient operation of a circuit design.
Hot-carrier degradation in NMOS and PMOS elements is, for example, a MOSFET wearout mechanism that can, over time, impact circuit performance in both CMOS and Bipolar or BICMOS operations (e.g., reduce the on-state current in an NMOS element and/or increase the off-state current in a PMOS element). Another example is NBTI. NBTI competes with bias-temperature degradation in PMOS elements during circuit operations and is a key process and design limiter in advanced CMOS technologies. NBTI is very dependent on temperature and gate bias. Hot-carrier and NBTI degradation contributions can be distinguished by stressing at different temperatures. In addition, in Bipolar transistors, beta degradation and electromigration induced stress build-up on the poly emitter may also affect overall circuit performance.
It is also well known that most of the degradation resulting from the various wearout mechanisms, and impacting circuit element operation, can be recovered or repaired via an appropriate high temperature bake. For example, U.S. Pat. No. 4,238,694 discloses a method for recovering selected areas of a radiation damaged semiconductor.
Drawbacks associated with the foregoing and other known healing or recovery techniques, include the need to electrically adjust the selected semiconductor device to be sensitive to a specific electronic healing mechanism, the limited application of healing only damage resulting from radiation, the lack of healing specificity in using thermal energy, and/or the inability to use repeatedly the particular recovery technique.
Thus, notwithstanding what is known, there remains a need for an efficient method and circuit that can provide localized thermal healing to recover specific elements in specific circuits damaged and/or aged by specific wearout mechanisms (e.g., hot-carrier, NBTI, etc.).